Field of the Invention
The invention relates to a rear hub suited in particular for mountain bikes and, in a particularly preferred embodiment, for downhill mountain bikes. The invention further relates to a corresponding bicycle axle.
Description of Related Art
With mountain bikes having a sprung rear wheel and a derailleur system, a rear wheel suspension structure is often chosen which stabilizes the suspension system upon acceleration, so that the wheel load change causes no compression of the spring (so-called anti-squat). In this regard it is known to use the chain pulling force for stabilization, so that a spring compression at the rear frame is prevented at least in part. In particular with downhill mountain bikes a structure is often chosen in which the wheel deflection trajectory of the rear wheel axle starts relatively flatly in the rearward direction. Thereby, the sprung rear wheel can be deflected better by large obstacles. Both the increase in chain pulling force and a corresponding wheel deflection trajectory cause an increase in the distance between the bottom bracket and the rear hub when the rear wheel is deflected. Since the pawls of the freewheel in the rear wheel couple the chain with the latter for rotation therewith, the increase in the distance between the bottom bracket and the rear hub results in reverse rotation of the chain blade and thus to a reverse rotation of the pedals. Since the cyclist represents the main mass of the system and the weight of the cyclist bears on the pedals in particular while riding off-road, such a pedal kickback is perceived by the cyclist as a spring hardening. In this moment, the chain tension prevents a free deflection of the rear frame structure and/or slipping occurs at the rear wheel's point of contact with the ground, since the rear wheel is driven abruptly by the chain. As a result, ground contact may be reduced. Further, the lateral guiding of the rear wheel is affected, i.e. the directional stability decreases.